In recent years, since mobile phones with various kinds of built-in sensors such as GPSs or the like have been widely used, it has been possible to collect daily action histories (life logs) such as the location information, the buying histories, and the like of users in real time on a server side. In addition, using these pieces of the information collected on the server side, a recommending service or the like in which recommended information is distributed to a user on the basis of the location or the preference of the user is being realized.
On the other hand, when information is provided to a service provider on the basis of these pieces of the life log information collected on the server side, it is necessary to protect privacy so that an individual is not identified on the basis of the provided information. In response, in a case in which a privacy information acquisition request (a request for location information) based on the location information is received from the service provider, only when there are plural users having the attribute value thereof, the number of the users being at least greater than or equal to K (the number satisfying a K-anonymity criterion), desired information is provided. In this way, Japanese Laid-open Patent Publication No. 2005-234866 discloses a method in which a privacy risk due to the limited number of users is solved owing to the reduced number of users to be dealt with.